Shelle Parsons Interference Fits for Bearings, Pins & Bushings A press fit (interference fit) is when the shaft is slightly larger than the hole, requiring force to assemble. The interference creates a clamping force between the parts — no fasteners needed. Getting the interference right is critical: too little and the part slips, too much and you … Read more
Reading Weld Symbols Weld symbols on engineering drawings tell the welder exactly what joint to make, where to put it, and how big it should be — without writing paragraphs of notes. The system is defined by AWS A2.4 and it’s more logical than it looks once you understand the structure. The Weld Symbol Structure … Read more
Bolt Clearance Hole Sizes When a bolt passes through a part without threading into it, the hole needs to be slightly larger than the bolt diameter. How much larger depends on how precisely the holes need to align. US Bolt Clearance Holes Bolt Size Close Fit (in) Normal Fit (in) Loose Fit (in) #4 (0.112) … Read more
Identifying Unknown Threads You found a bolt. You don’t know what it is. Here’s how to figure it out in 60 seconds with a thread pitch gauge, a caliper, and this chart. Step 1: Measure the Major Diameter Use a caliper to measure the outside diameter of the bolt threads. This tells you whether you’re … Read more
What is Tolerance Stack-Up? When multiple parts assemble together, each dimension has a tolerance. Those tolerances accumulate. Tolerance stack-up analysis tells you whether your assembly will work — or whether you’ll be forcing parts together on the shop floor. There are two fundamental approaches: Worst Case (everything goes wrong simultaneously) and RSS/Statistical (realistic probability-based analysis). … Read more
Choosing the Right Stainless Steel There are over 150 grades of stainless steel. In practice, you’ll use about five of them 90% of the time. This guide covers those five — when to use each, what to watch out for, and the trade-offs between them. The Big Five — Quick Comparison Property 304 316 303 … Read more
Common Aluminum Alloys for Engineering Not all aluminum is the same. The alloy designation tells you everything about its strength, machinability, weldability, and corrosion resistance. Here’s the practical comparison for the alloys you’ll actually encounter. Properties Comparison Table Property 6061-T6 7075-T6 2024-T3 5052-H32 Tensile Strength (ksi) 45 83 70 33 Yield Strength (ksi) 40 73 … Read more
Standard Bolt Torque Values These are recommended tightening torques for standard dry (unlubricated) bolts. If you’re using lubricant, anti-seize, or plating, reduce torque by 25–30% — lubrication dramatically changes the torque-tension relationship. Grade 5 Bolts — Torque Values Bolt Size TPI (UNC) Clamp Load (lbs) Torque Dry (ft-lbs) Torque Lubed (ft-lbs) 1/4-20 20 2,025 6.3 … Read more
Socket Head Cap Screw (SHCS) Dimensions Socket head cap screws are the go-to fastener for machine design. Their cylindrical head fits into a counterbore, allowing the screw to sit flush with or below the surface — critical when you need clearance for moving parts or a clean look. All dimensions per ASME B18.3: Screw Size … Read more